Currently, the wireless communication technology is subjected to some limitations, such as limited bandwidth and transmission power, interference, signal attenuation, multipath effect, and Doppler effect caused by a higher moving speed of a user equipment. With a further deepening and development of investigation, the combination system of a wideband wireless mobile and a wireless access of future mobile communication becomes a hot research project currently, and a MIMO (Multiple Input Multiple Output) system is one of hot topics researched by people. The basic principle of the MIMO is to use a plurality of antennas at a transmitter, a receiver, or both the transmitter and the receiver, by a space-time processing technology, to take full advantage of independent fading characteristics among channels, so as to improve spectrum efficiency, communication quality and system capacity.
Space-time coding is the basis of the MIMO system, the space-time coding technology maps, according to a certain design rule, coding redundant information to a two-dimensional time-space plane as evenly as possible by taking advantage of an orthogonality or a quasi-orthogonality between a space domain and a time domain, so as to decrease the effect of a time-selective fading and a space-selective fading caused by a wireless multipath propagation, thus to achieve high speed data transmission with high reliability in wireless channels. Alamouti proposed a STBC (Space Time Block Coding) based on two transmission antennas in 1998; and since this solution can greatly improve the quality of receiving links in a fading channel, is easy to be realized and makes the complexity of the decoding of the receiver to be lower, it is adopted by protocols such as 3GPP (3rd Generation Partnership Project) and IEEE (Institute for Electrical and Electronic Engineers) 802.16. However, the coding solution of Alamouti requires that it is supposed a channel keeps constant at two time points, therefore, SFBC (Space Frequency Block Coding) is more stable in a fading environment compared with the STBC which can keep performance only in a low fading environment; and the SFBC, which is a multicarrier technology applied to neighboring sub-channels or neighboring carriers, is more suitable for being used in a LTE multicarrier modulating system based on an OFDM (Orthogonal Frequency Division Multiplexing) technology.
FIGS. 1a and 1b are block diagrams showing the principles of diversity transmission methods in a LTE wireless communication system under a 2-port situation and a 4-port situation respectively. Different from the situation in which a diversity gain is obtained without impairing data rate by using two antennas, when a transmit diversity mode is used by 4 transmission ports, N code elements need 2N sub-carriers, which results in a reduction in the data rate. In order to realize a full rate transmission in a transmit diversity mode of the LTE system via multiple ports, the protocols regulate that the downlink transmit diversity solution based on SFBC+FSTD (Frequency Switched Transmit Diversity) is employed for the 4-port situation. Therefore, if the traditional demodulating method based on the 2-port is directly applied to the 4-port mode, performance loss will occur; and if a method of directly inversing a coding matrix is used, the complexity of the downlink demodulation algorithm will increase sharply.
Therefore, it is necessary to provide a new solution to overcome shortcomings in the related art.